#1731 web: the unlabelled sparklines were scaled by their own noise

Beschreibung

spark(id, values, max) sets the axis top to max(|max|, the series' own
maximum, 1e-9).  gpu_util, temperature, cpu, vram and power pass an
explicit maximum, but the pcie, tok/s, prefill and disk cards do not, so
those axes zoom onto whatever the series happens to hold.

An idle amdgpu pcie counter reads 0.01-0.02 MB/s (50 packets x 256 B per
second), and that becomes a full-amplitude square wave in the Monitor
while the tile's own text says 0.0 MB/s.  Measured in the live DOM: the
pcie line's y values are only {4.0, 30.0}, i.e. the baseline and the top.

A floor of 1 only ever lowers the axis - the series maximum still wins -
so a real burst keeps its scale, and the cards that pass a maximum are
untouched.